nhttp_qpack_encoder (nhttp_lib v1.0.0)
View SourceQPACK encoder state machine (RFC 9204 Section 2.1).
Converts field sections into compressed representations using the QPACK header compression format for HTTP/3. The encoder maintains a dynamic table, generates encoder stream instructions for table modifications, and produces encoded field section data for request streams.
The implementation uses a conservative encoding strategy following Appendix C of RFC 9204: static table lookups are always preferred, dynamic table entries are only referenced when safely below the Known Received Count (no risk of blocking), and new entries are inserted eagerly when table capacity allows.
Usage
{ok, Enc0} = nhttp_qpack_encoder:new(#{
max_table_capacity => 4096,
max_blocked_streams => 100
}),
Headers = [{<<":method">>, <<"GET">>}, {<<":path">>, <<"/">>}],
{ok, Enc1, EncStreamData, FieldData} =
nhttp_qpack_encoder:encode_field_section(Enc0, 0, Headers),
DecoderData = ...,
{ok, Enc2} = nhttp_qpack_encoder:feed_decoder_stream(Enc1, DecoderData).Summary
Functions
Encode a field section for the given stream.
Process decoder instructions received on the decoder stream. Handles section acknowledgments, stream cancellations, and insert count increments. Partial instructions are buffered (returns the current state unchanged).
Create a new encoder with the given configuration.
Reconcile the encoder against the peer's advertised QPACK limits
(RFC 9204 Section 3.2.3). The peer is the decoder of the field
sections this encoder produces, so the effective dynamic-table
capacity is bounded by min(configured ceiling, peer advertised), and
the encoder must never reference more than the peer's advertised
blocked-stream budget. max_entries for the field-section prefix is
fixed by the peer's advertised capacity (Section 4.5.1.1), independent
of how much of the table this encoder chooses to use.
Types
-type config() :: #{max_table_capacity => non_neg_integer(), configured_max_capacity => non_neg_integer(), max_blocked_streams => non_neg_integer(), configured_max_blocked => non_neg_integer(), huffman => boolean()}.
-opaque state()
Functions
-spec encode_field_section(state(), nhttp_lib:stream_id(), [{binary(), binary()}]) -> {ok, state(), iodata(), iodata()}.
Encode a field section for the given stream.
Returns encoder stream data (instructions for the decoder's dynamic table) and field section data (the prefix plus encoded representations to send on the request stream).
Process decoder instructions received on the decoder stream. Handles section acknowledgments, stream cancellations, and insert count increments. Partial instructions are buffered (returns the current state unchanged).
Create a new encoder with the given configuration.
-spec reconcile_peer_limits(non_neg_integer(), non_neg_integer(), state()) -> state().
Reconcile the encoder against the peer's advertised QPACK limits
(RFC 9204 Section 3.2.3). The peer is the decoder of the field
sections this encoder produces, so the effective dynamic-table
capacity is bounded by min(configured ceiling, peer advertised), and
the encoder must never reference more than the peer's advertised
blocked-stream budget. max_entries for the field-section prefix is
fixed by the peer's advertised capacity (Section 4.5.1.1), independent
of how much of the table this encoder chooses to use.
Arms the Set Dynamic Table Capacity instruction so the next encode announces the effective capacity on the encoder stream before any reference to a dynamic entry. Capacity 0 (the QPACK default, e.g. a peer that does not advertise the setting) leaves the encoder dormant: all field lines stay static-or-literal and no encoder-stream instructions are emitted.